Top Soil

taras49(6)August 20, 2012

I built an 8' x 8' raised garden bed last year. I filled it with 75 bags of inexpensive top soil, bought from Home Depot. My vegetables did well last year but this year not so good. For next year I'm thinking that I should buy a few large bags of "Garden Soil" and mix it in with my older top soil. Will this be beneficial? Was using just top soil a mistake?

YES it was:( and buying garden soil isn't going to be much better...my instict tells me do a soil test,find out what's like add ton of compost...I'm not an expert but I have read similar questions around here,I should let the experts speak:)

Beneficial? Well it can't hurt but it won't make much difference. Better to spend the money on lots and lots of quality compost and composted manure.

A mistake? Yes, unfortunately it was. No more than 50% of the bed should be top soil is the standard recommendation so now you have to correct the mistake and spend more money to do that. Pull up all the discussions here about how to build/fill raised beds - there are many of them - for all the details.

I'm no expert, but I work with soil types and farming, I'll try and explain.

Top Soil in this country formed under thousands of years of grasslands dying every winter, and the dying material and root growth breaking down into rich humus. Or in the case of wooded uplands, fallen trees and leaves breaking down into organic matter.

Without knowing specifics or fertilizer types used, I would say that you are starting to deplete your soil fertility. Fruit intensive crops will, through the course of producing, use Nitrogen, Phosphorous, and Potassium in order to produce high yields. They will also use micro nutrients, that is other minerals needed in much smaller ammounts, like iron, copper, manganese, cobalt, moly, and a couple of others. When you grow vegetables, which humans have bred to produce far more fruit per plant than nature ever intended, they will need more nutrients in the soil to produce them.

Most of the nutrients that plants require can be found in other plants, so taking weeds and composting them would be beneficial. Animal manure like horse or cattle is even better, as they eat plant material and only absorb a fraction of what they ingest, making their manure prized garden gold for use in vegetable gardens. Be sure to hold off on adding fresh manure onto growing plants, the N content in fresh manure will be too high for most plants to tolerate. Animals are essentially giant nutrient factories for plants.

In gardening, you also have to note your pH levels. pH is a function of the concentration of positively charged hydrogen in your soil. Most micro nutrients have a negative charge, so when the pH is high, when there are a lot of positively charged hydrogen ions in your soil, nutrients like iron (which are negatively charged) will bond with the hydrogen and become unavailable to your plants. The best pH range for plants is in the neighborhood of pH 6.2-6.5. At that pH plant growth is fastest, and nutrient uptake is maximized.

With that kind of background I can assume two things, just shooting in the dark: Your soils probably need to be fertilized, and your pH might need to be lowered. Top Soil from most midwestern states formed under limestone, and they tend to be slightly alkaline, a higher pH. Top Soil from out east, especially in the south is more acidic. There's no way to know what you've got unless you test it. Your local county Farm Service Agency or county Natural Resources Conservation Service will have a list of places that offer soil testing for very modest fees. I recommend against do it yourself kits, as they require you to add a special dye to a soil/water suspension, and have you judge the shade of the color of the suspension against a color chart - very subjective.

I have no way of knowing what your issue is, because I don't know the particulars of your situation. Organic sources of fertilizer work slowly, and require microbial activity to release nutrients. Inorganic sources of fertilizer work quickly and efficiently, and they can lower a soil's pH over time.

It's hard to know the correct advice to give to you without knowing what you like to grow and if you have fertilized. Itzy is correct in her assertion that compost is always a good thing to add to soils. I could go into another paragraph about organic matter, but I won't.

Ground level or not, if you have simple dirt in there and you have all the problems one would have if one had not raised it up.
There IS NO MAGIC in raising a garden off the ground, the difference is in what is usually used as a growing compound.
You have the same stuff ground-level gardens use.

Some people with clay sometimes raise a garden, no boards or other tricks, just raise it, to get better drainage.
I have done this in a small area for a few things but do not treat it any differently than I do the hundreds of square feet at ground level.

Other than esthetics and relief from a bad back (less bending with a raised bed) what are the benefits from a raised garden when done correctly? My mistake, being a novice gardener was in thinking that top soil was the MAGIC that I had thought it would be.

If your soil is very clay and hard to work, raised gardens are often a must (as it is in my case). Go to Home Depot and get some bags of composted steer or chicken manure and work it into the soil. Last time I checked the steer manure was pretty cheap, about $1 per 1 cu. ft. That will help a lot.

I think the top soil bags sold at the big box stores are very poor quality. They are okay for a bag or two but 75 bags of it is too much poor soil. Next time check with local garden supply companies. They can deliver locally excavated/screened soil and for a small additional charge have finished compost mixed in (usually called "planters mix). It's more economical too usually 25-40$ per yd. plus delivery...

I just measured my small raised bed and it's dimension are 6.5' x 9' x 1'. If my calculations are right it comes out to about 2 cubic yards of the new top soil. How much fertilizer do you think I would need and when should I add the fertilizer, this fall or in the spring?

A good rule of thumb would be going to the local farm supply store and getting a couple of bags of granulated 10-10-10 fertilizer, and apply a little this fall to your raised beds, along with leaf and grass clippings, some peat moss, horse manure/bedding if you can find it.

Then in the spring, adding a fair ammount of the fertilizer to the beds. If your pH is right, you'll only have to fertilize at the beginning of the year, and the soils should retain the nutrients well into August.

If you add a lot of organic matter to the soil in the spring it will start to break down in the soil, and the soil bacteria that break it down will tie up some N while they break it down, you might have to add some more Nitrogen during the growing season. Adding organic matter in the fall and letting the soil microbes work on it through the winter should give it plenty of time to avoid Nitrogen tie up next year.

As for how much to add, it's a judgement call. A little bit of granular goes a long way, and eyeballing it should be sufficient for what you want. Just spread a moderate ammount, or if you are that worried, measure out the weight according to what your soil test says to add. For Potassium and Phosphorous, if you add a little too much of it, that's ok, as any extra P and K that isn't used by your plants will stay in the soil until next year. Any extra N will be eaten by Nitrobacter by the time next spring rolls around, so you won't get any carryover.

If you do add organic matter to the soil this fall, it would help to add *some* nitrogen to the soils to help in the breakdown process, because the bacteria that break down organic matter require N to do the job. The neat thing is that they release the N that they use back into the soil when they are done breaking down the organic matter.

Well this is my problem. I'm disabled and on a very fixed income. My caregiver thought just using topsoil and shake on vegetable food would do it. My plants are already in the raised beds and have been for a couple of weeks. The peas and the beans seem to love it. But the watermelon, cucumber, dill and crookneck squash are having a very hard time. The jury is out on the tomatoes. The cauliflower seems to be doing ok...What can I do to save my garden? BTW I do not know exactly what zone I'm in. This site says 8, National Garden Assoc says 7b, Arbor Day Assoc says 9 and Sunset magazine says 5. I live in Charleston Oregon (Coos Bay). Thank you and Great Gardening!

It all depend on the quality of top soil. Every general soil sold in bags are labeled top soil. NOT all top soils are GARDEN soil. To make a general top soil into garden soil you have to mix it with compost (50/50 , give or take 1%). adding composted manure further can improve it.

You can find out how good or bad your garden soil is by trial and error. That will require one season and may cost all your wasted efforts and time. Then you can have you garden soil tested for pH, and nutrients. This way you are pretty much set.

My friend did exactly what you did with similar results. We took a soil sample in to our Extension Agent and it came back as high in Phosphorous and Potassium and virtually no nitrogen.

I have raised beds and I love them. They provide perfect drainage, I can plant intensively in them while still being able to work them without compacting the soil. I don't waste fertilizers or amendments because I am only putting them on growing space, not paths. They warm up earlier in the spring too. I could go on and on.

Don't give up on raised beds, just concentrate on improving the soil in them. If you built them on top of your native soil, you would do well to double dig them and bring some of your native soil up into the container. My native soil is horrible tight red clay. It was a pain to dig it in, but it is nutrient rich and as I worked it with the compost and manure that I used to fill my beds, it began to break down. It has virtually perfect tilth now. It just takes takes time with your shovel to get there.

Another thing you could do is to sow a cover crop (I love red clover.) in your beds this fall. Then next year about a month before planting time take your shovel and turn it into the soil. You'll be amazed at what a big difference it will make in the structure of your soil as well as the nutrition in it.

Is there a way I can still save my plants? I got some garden soil and have miracle grow. Can I Either water the plants with miracle grow or dig in garden soil. I lost some of the cucumbers and all the watermelons today. I did take 4 of the cucumbers and repotted them in huge containers a couple of days ago and watered them with the miracle grow and they seem to be looking better today. They are lemon cucumbers (I love them so much). We live on such a limited budget (less than $800 a month between the two of us due to disabilities for both of us) that adding expensive compost is not cost effective for us. I sure would like to see at least a few of them make it. Now I did put my potatoes directly in the ground and they seemed to be doing great. I also put the following directly in the ground as well: Several varieties of tomatoes, zucchini, crook neck, raspberries and a couple of cauliflower as well. Before I did that I mixed about 40% of miracle grow garden soil with it. I sure wished I didn't look stupid doing this. But I want to thank all that has tried to help me

I have a suggestion: For cucumbers, melons ... dig a circle around each (about 16" in diameter, 2 to 3 inches deep, and about 3" wide ). be careful not to hit any roots. Then get manure compost and fill that doughnut shape hole. You can sprinkle and mix a little bit of all purpose time release fertilizer too. Cover it wit 1/2" soil, water it. Depending on the strength of manure, that should take care of that plant for 3 to 4 weeks.

REMEMBER: Soil is just a medium. It can be anything as long as it provides: balanced moisture retention and drainage. Then you add nutrients to that medium . That is all plants care about. Obviously inorganic soil (debris from the rocks, stones ... ) are plentiful. Then you have to adjust its pH and add nutrients to it. Topsoil is mostly inorganic soil with some organic matter accumulated over time. So , adding compost to any soil can make it garden soil.